Recently, electrolytic solutions which maintain their specific conductivity at 4 mS/cm or more and simultaneously have a high sparking voltage have increasingly been desired with increase in working voltage of power supplies for vehicle-mounted electrical components and digital home appliances.
As such an electrolytic solution for aluminum electrolytic capacitors, an electrolytic solution containing an organic solvent and an electrolyte composed of phthalic acid and a quaternary salt of a compound having an N,N,N′-substituted amidine group (e.g., 1-methylimidazole and 1,2-dimethylnmidazoline) is known (see patent document 1).
On the other hand, an electrolytic solution containing an organic solvent and an electrolyte composed of a tetrafluoroaluminate ion is known (see patent document 2).    [Patent document 1] WO 95/15572    [Patent document 2] JP2003-142346A